Three-phase Composites Research Articles

Interphase Model for Effective Moduli of Nanoparticle-Reinforced Composites

AbstractA novel interphase model is constructed based on the double-inclusion theory and the Eshelby tensor in a finite domain, which can be used to calculate the effective material properties of three-phase composites. The refinement of the double-inclusion theory takes into account the effect of a finite matrix and that of a finite interphase. In the model proposed, the multiphase composites are reinforced by different material fillers, which are embedded in a matrix with finite size. The general formulations are derived following the method of Eshelby’s equivalent inclusion. The Dirichlet and Neumann Eshelby tensors for a spherical inclusion in a finite spherical domain are applied to the homogenization of composite materials. By the explicit inversions of the fourth-order tensors involved, the relationships between the elastic moduli of transversely isotropic and orthotropic materials are derived, which are then validated through numerical results from the homogenization of several Al2O3/mullite/Al co...

Effect of borojo (Borojoa patinoi Cuatrecasas) three‐phase composition and gum arabic on the glass transition temperature

The search for natural, novel, high-quality, stable food ingredients is an ongoing practice in the food industry. Pulp of borojo (Borojoa patinoi Cuatrecasas), which is a fruit of the Colombian Pacific region, can be separated into three phases: liquid (LP), medium (MP) and solid (SP) phases. The objective of this work was to evaluate the effect of the three-phase composition and gum arabic on their glass transitions temperatures (T(g)). The best mixture, LP-MP, MP-SP and LP-SP and gum arabic (GA) was identified by response surface methodology. When adding GA to SP borojo phase in a 1:1 proportion, the resulting T(g) of the mixture was 132.27 °C whereas Tg for GA and SP-phase were 154.89 °C and 79.86 °C respectively, which supported this combination as attractive from a processing perspective and supports an industrial advantage of using borojo as food ingredient. Phases were characterized by high-performance liquid chromatography, Fourier transform infrared spectroscopy, confocal laser scanning microscopy and mass spectrometry. Low molecular weight compounds such as fructose for MP lowered T(g) whereas the presence of lignin increased T(g) of the mixtures as with the SP. The addition of GA significantly increased T(g) of borojo phases so leading to propose them as novel food processing materials.

A meso-scale approach to modeling thermal cracking of concrete induced by water-cooling pipes

Cooling by the flow of water through an embedded cooling pipe has become a common and effective artificial thermal control measure for massive concrete structures. However, an extreme thermal gradient induces significant thermal stress, resulting in thermal cracking. Using a mesoscopic finite-element (FE) mesh, three-phase composites of concrete namely aggregate, mortar matrix and interfacial transition zone (ITZ) are modeled. An equivalent probabilistic model is presented for failure study of concrete by assuming that the material properties conform to the Weibull distribution law. Meanwhile, the correlation coefficient introduced by the statistical method is incorporated into the Weibull distribution formula. Subsequently, a series of numerical analyses are used for investigating the influence of the correlation coefficient on tensile strength and the failure process of concrete based on the equivalent probabilistic model. Finally, as an engineering application, damage and failure behavior of concrete cracks induced by a water-cooling pipe are analyzed in-depth by the presented model. Results show that the random distribution of concrete mechanical parameters and the temperature gradient near water-cooling pipe have a significant influence on the pattern and failure progress of temperature-induced micro-cracking in concrete.

Meso-scale modeling of chloride diffusion in concrete with consideration of effects of time and temperature

A meso-scale truss network model was developed to predict chloride diffusion in concrete. The model regards concrete as a three-phase composite of mortar matrix, come aggregates, and the interfacial transition zone (ITZ) between the mortar matrix and the aggregates. The diffusion coefficient of chloride in the mortar and the ITZ can be analytically determined with only the water-to-cement ratio and volume fraction of fine aggregates. Fick's second law of diffusion was used as the governing equation for chloride diffusion in a homogenous medium (e.g., mortar); it was discretized and applied to the truss network model. The solution procedure of the truss network model based on the diffusion law and the meso-scale composite structure of concrete is outlined. Additionally, the dependence of the diffusion coefficient of chloride in the mortar and the ITZ on exposure duration and temperature is taken into account to illustrate their effect on chloride diffusion coefficient. The numerical results show that the exposure duration and environmental temperature play important roles in the diffusion rate of chloride ions in concrete. It is also concluded that the meso-scale truss network model can be applied to chloride transport analysis of damaged (or cracked) concrete.

Enhancement of dielectric and electrical properties in BT/SiC/PVDF three-phase composite through microstructure tailoring

A polymer composite with high dielectric permittivity was prepared by embedding silicon carbide (SiC) whisker with an average diameter of 500nm–1μm in poly(vinylidene fluoride) (PVDF). However, the high dielectric loss and electrical conductivity of the two-phase composite prohibits its potential applications. Barium titanate (BT) particles with average diameter of 100nm and 1μm were incorporated as a third phase to fabricate a three-phase composite. The morphology structure, dielectric and electrical properties before and after the addition of BT particles were investigated. The three-phase composite exhibits largely suppressed dielectric loss and electrical conductivity without sacrificing the high dielectric permittivity, which was extremely hard to be realized for two-phase composite. It is also found that the nano-size BT is more favorable in achieving high dielectric permittivity than the micro-size BT, where their dielectric loss and electrical conductivity are similar. Furthermore, electric modulus analysis confirms the largely suppressed electron conduction process which results in the enhanced dielectric and electrical properties in three-phase composite.

Rheology, crystallization behavior, and dielectric study on molecular dynamics of polypropylene composites with multiwalled carbon nanotubes and clay

The study is focused on joint effects of two nanofillers in polypropylene (PP) reinforced with 3 wt% organo-clay (ОC) and 0.1–5 wt% multi-wall carbon nanotubes (MWCNTs). The composites were produced by extrusion and characterized by rheology, differential scanning calorimeter (DSC), thermally stimulated depolarization currents (TSDC), and dielectric relaxation spectroscopy (DRS). Rheological data indicates а formation of a network structure related to percolation above 1 wt% nanotubes. The flow activation energy (Ea) decreases above the percolation threshold, thus, the presence of clay improves the debundling of MWCNTs and releases the segmental motion of polymer chains. The clay does not affect the crystallization behavior of PP, but the nucleation is enhanced strongly by the MWCNTs. Dielectric measurements reveal that the presence of clay affects the molecular mobility of PP at the amorphous phase. The DSC results imply that around 80°C a cold crystallization process occur in the PP phase which has a significant impact on the dielectric segmental relaxation process and gives rise to the appearance of an additional process, the so called “interfacial” relaxation process. This new relaxation process in the three-phase composites was attributed to an interfacial polarization process due to blocking of charge carriers at polymer/clay interfaces. POLYM. COMPOS., 37:2756–2769, 2016. © 2015 Society of Plastics Engineers

Inter-Carbon Nanotube Contact and Thermal Resistances in Heat Transport of Three-Phase Composites

Single-walled carbon nanotubes (SWNTs) tend to aggregate into bundles due to van der Waals forces during the fabrication of the composite. A computational model using an off-lattice Monte Carlo method is developed to systematically investigate the effects of SWNT bundles, the number of SWNTs per bundle and the thermal boundary resistance (TBR) at the SWNT–SWNT interfaces on the effective thermal conductivity (Keff) of three-phase composites. It is found that the aggregation of the SWNTs in bundles can reduce significantly the Keff of the composites with SWNTs oriented parallel or randomly to the heat flux direction, but it enhances slightly the Keff of those with SWNTs perpendicular to the heat flux direction. The Keff of the composites also decreases when more individual SWNTs aggregate in each bundle and with larger SWNT–SWNT TBR values. The thermal transport mechanism within the composites is dominated by a critical SWNT–SWNT TBR of 0.155 × 10–8 m2K/W.

Improved microwave absorption and electromagnetic properties of BaFe12O19-poly(vinylidene fluoride) composites by incorporating reduced graphene oxides

Three-phase composites of poly(vinylidene fluoride)-BaFe12O19-reduced graphene oxide (PVDF–BFO-RGO) were synthesized by a facile wet chemical method and hot-pressing approach. The phase structure, topography of the hybrid materials were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectra. Influence of RGO on their electromagnetic properties was investigated. Especially, improved microwave absorption and electromagnetic properties of BaFe12O19–PVDF composites by incorporating RGO were obtained and studied. The PVDF/BFO/RGO sample with m(RGO):m(BFO) = 5:100 shows the best microwave absorption properties with a minimum RL = −32 dB at 11 GHz and with the bandwidth less than −20 dB from 9.6 to 12.8 GHz. The composites were believed to have potential applications as the microwave absorber.

A micro-macro model for time-dependent behavior of clayey rocks due to anisotropic propagation of microcracks

In this paper, a micro-macro model is proposed for the time-dependent behavior of clayey rocks. Two material scales are considered. At the mesoscopic scale, the studied material is represented by a three-phase composite. Quartz and calcite grains are embedded inside the clay matrix. At the microscopic scale, the clay matrix is characterized by a cracked elastic solid. The creep deformation is assumed to be induced by the time-dependent propagation of anisotropic microcracks inside the clay matrix. A two-step homogenization procedure is proposed. The effective elastic properties of the cracked clay matrix are first determined using an Eshelby solution based homogenization method. Two different homogenization schemes are used respectively with and without taking into account crack interactions. Then the macroscopic mechanical properties of heterogeneous clayey rocks are determined by the second homogenization step using the Mori Tanaka Scheme. A sensitivity study is performed in order to evaluate macroscopic consequences of the microscopic time-dependent propagation law of microcracks. Finally, comparisons between numerical results and experimental data from creep tests are presented.

Enhanced dielectric performance of three phase percolative composites based on thermoplastic-ceramic composites and surface modified carbon nanotube

Three-phase composites were prepared by embedding CaCu3Ti4O12(CCTO) nanoparticles and Multiwalled Carbon Nanotube (MWNT) into polyimide (PI) matrix via in-situ polymerization. The dependences of electric and dielectric properties of the resultant composites on volume fractions of filler and frequency were investigated. The dielectric permittivity of PI/CCTO-surface modified MWNT (MWNT-S) composite reached as high as 252 at 100 Hz at 0.1 vol. % filler (MWNT-S), which is about 63 times higher than that of pure PI. Also the dielectric loss is only 0.02 at 100 Hz. The results are in good agreement with the percolation theory. It is shown that embedding high aspect ratio MWNT-S in PI/CCTO composites is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

Abrasive wear in three-phase waste-based polymeric particle composites

Abrasive wear in three-phase waste-based polymeric particle composites

The influence of inducing magnetic field on the magnetoelectric effect of particulate magnetoelectric composites

The magnetoelectric effect in a three-phase particulate magnetoelectric composite is experimentally studied with specific interest in the dependence on the inducing magnetic field up to 300Oe. A particulate magnetoelectric composite consisting 30vol% of PVDF, 63vol% of PZT and 7vol% of Terfenol-D is fabricated in lab followed by the inducing magnetic field along the diameter direction in the process of hot pressing. It is observed that the change of inducing magnetic field influences the value of the magnetoelectric coefficient. This is partly attributed to the oriented domain walls promote the increase of the magnetostrictive coefficient of Terfenol-D, and partly attributed to the contraction deformation of Terfenol-D which causes the decrease of the coupling coefficient between PZT, TD and PVDF, which together influence the change of the magnetoelectric coefficient. In addition to the inducing magnetic field, the influence of the bias magnetic field in the process of testing to the magnetoelectric coefficient is examined at different fixed resonance frequency. A maximum of magnetoelectric coefficient 82.58mV/(cmOe) is obtained when the inducing magnetic field Hi=200Oe and the bias magnetic field Hdc=1000Oe. When Hi<200Oe, the increase of the magnetostrictive coefficient of Terfenol-D plays a leading role which leads to increasing magnetoelectric response. In the Hi range of 200Oe<Hi<300Oe, the decrease of the coupling coefficient between PZT, TD and PVDF plays a leading role and the magnetoelectric coefficient drops along the increase of the inducing magnetic field.

A model for evaluation of effective thermal conductivity of periodic composites with poorly conducting interfaces

This paper presents a new micromechanical extension of the parametric finite-volume theory for evaluation of effective thermal conductivities of periodic unidirectional fiber reinforced composites. Such materials are assumed as composed of repeating unit cells with arbitrary internal architectural arrangements of fiber coated by thin interphase with low thermal conductivity. The parametric homogenization approach uses quadrilateral subvolumes for discretization of the repeating unit cell microstructure, thereby allowing an efficient modeling of the details of fibers with arbitrarily shaped cross sections. The interphases are replaced by imperfect interface elements with continuity in normal heat flux and discontinuity in temperature. The performance of the homogenization model is demonstrated for several numerical examples, including two-and three-phase composites with regular squared and hexagonal arrays of fibers. The ability of the model to accurately predict the effective thermal conductivity of those composites is demonstrated by means of comparisons of results obtained using finite-element and analytical solutions.

Fabrication and characterization of Ba0.5Sr0.5TiO3-PANI/PS three-phase composites

Ba0.5Sr0.5TiO3 particles with perovskite phase were successfully synthesized by molten salt assisted co-precipitation using inexpensive TiOSO4 as raw material. The effect of the amount of molten salt on the formation, morphology, and dielectric properties of Ba0.5Sr0.5TiO3 particles was investigated. Ba0.5Sr0.5TiO3-polyaniline (PANI) hybrid particles were then synthesized by in situ polymerization of aniline with Ba0.5Sr0.5TiO3. The obtained Ba0.5Sr0.5TiO3-PANI hybrid particles were characterized through thermogravimetry (TG), X-ray diffraction (XRD), Fourier-transform-Infrared (FT-IR) and scanning electron microscopy (SEM). The three-phase composites by incorporating Ba0.5Sr0.5TiO3-PANI hybrid particles in Polystyrene (PS) matrix were demonstrated. SEM showed that the Ba0.5Sr0.5TiO3-PANI hybrid particles were distributed in the continuous PS matrix heterogeneously without obvious aggregation. Moreover, the glass transition temperature and thermal stability of composites were improved with the addition of hybrid particles. The three-phase composites were attractive candidate as embedded capacitors.

Thermal measurements and computational simulations of three-phase (CeO2–MgAl2O4–CeMgAl11O19) and four-phase (3Y-TZP–Al2O3–MgAl2O4–LaPO4) composites as surrogate inert matrix nuclear fuel

This study investigates the temperature dependent thermal conductivity of multiphase ceramic composites for simulated inert matrix nuclear fuel. Fine grained composites were made of CeO2–MgAl2O4–CeMgAl11O19 or 3Y-TZP–Al2O3–MgAl2O4–LaPO4. CeO2 and 3Y-TZP are used as UO2 surrogates due to their similar structures and low thermal conductivities. Laser flash analysis from room temperature to 1273K (1000°C) was used to determine the temperature dependent thermal conductivity. A computational approach using Object Oriented Finite Element Analysis Version 2 (OOF2) was employed to simulate the composite thermal conductivity based on the microstructure. Observed discrepancies between experimental and simulated thermal conductivities at low temperature may be due to Kapitza resistance; however, there is less than 3% deviation between models and experiments above 673K (400°C) for both compositions. When the surrogate phase was replaced with UO2 in the computational model for the four-phase composite, a 12–16% increase in thermal conductivity resulted compared to single phase UO2, in the range of 673–1273K (400–1000°C). This computational approach may be potentially viable for the high-throughput evaluation of composite systems and the strategic selection of inert phases without extensive sample fabrication during the initial development stages of composite nuclear fuel design.

Antiplane magneto-electro-elastic effective properties of three-phase fiber composites

In the present work, applying the asymptotic homogenization method (AHM), the derivation of the antiplane effective properties for three-phase magneto-electro-elastic fiber unidirectional reinforced composite with parallelogram cell symmetry is reported. Closed analytical expressions for the antiplane local problems on the periodic cell and the corresponding effective coefficients are provided. Matrix and inclusions materials belong to symmetry class 6mm. Numerical results are reported and compared with the eigenfunction expansion-variational method (EEVM) and other theoretical models. Good agreements are found for these comparisons. In addition, with the herein implemented solution, it is possible to reproduce the effective properties of the reduced cases such as piezoelectric or elastic composites obtaining good agreements with previous reports.

Influences of reinforcing particle and interface bonding strength on material properties of Mg/nano-particle composites

In the present study, an effective model is proposed to predict the effective elastic behavior of the three-phase composite containing spherical inclusions, each of which is surrounded by an interphase layer. The constitutive equations are derived for the stress and strain of each phase of the composite subjected to a far-field tension. Based on these constitutive laws, the effective bulk, shear and Young’s modulus are obtained. A statistical debonding criterion is adopted to characterize the varying probability of the evolution of interphase debonding. Influences of debonding damage, particle volume fraction, interphase properties and bonding strength on overall mechanical behavior of composites are also discussed. Numerical analyses are carried out on particle-reinforced composites and the predictions have a good agreement with the experimental results.

Analysis on the process of stress transferring and characterization on the property of “interphase” in three-phase single-fiber composites

In this study, two micro-mechanical models for analyzing the stress transferring in single-fiber composites composed of the fiber, the matrix, and the interphase are developed based on the shear-lag theory. The analytical model has taken into account two micro-damage modes, that is, the interficial debonding and the matrix damage, respectively. So, the real distribution of the shear stress at the interface and the axial stress in the fiber in single-fiber composites under loading can be obtained. An approach based on combining the micro-mechanical model with the single-fiber fragmentation test was utilized to determine the property of the interphase. The more accurate and real shear strength of the interphase in single-fiber composites is determined compared with the previous methods.

On the shape of effective inclusion in the Maxwell homogenization scheme for anisotropic elastic composites

The paper focuses on the main uncertainty involved in classical Maxwell’s (1873) homogenization method for elastic composites. Maxwell’s scheme that equates the far fields produced by a set of inhomogeneities and by a fictitious domain with unknown effective properties (“effective inclusion”) is re-written in terms of the compliance and stiffness contribution tensors. It is shown that the shape of the effective inclusion substantially affects the overall elastic properties. The choice of this shape in the case of anisotropic composite is a non-trivial problem that has never been discussed in literature. In this paper, we show that the problem appears due to incompleteness of the Maxwell scheme and show that the problem can be realized when the effective inclusion is of ellipsoidal shape. We discuss how the aspect ratios of the ellipsoid have to be chosen and illustrates the approach by two examples – material with cracks having orientation scatter and a three-phase transversely-isotropic composite. It is also shown that tensor of the effective elastic constants calculated in the framework of Maxwell’s scheme is always symmetric with respect to couples of indices.

Large self-biased effect and dual-peak magnetoelectric effect in different three-phase magnetostrictive/piezoelectric composites

We investigate magnetoelectric (ME) effects in various three-phase laminate composites of FeCuNbSiB/Terfenol-D/PZT(FeMP), FeCuNbSiB/iron–nickel-based ferromagnetic alloy with constant elasticity/PZT(FeFP) and FeCuNbSiB/Ni/PZT(FeNiP). Under the low frequency and resonant frequency condition, various composites exhibit hysteretic ME responses as a function of applied bias field. Both self-biased effect characterized by non-zero ME effect at zero bias and dual-peak ME effect are observed. Especially, self-biased ME properties are remarkably enhanced at resonance. The zero-biased ME coefficient for FeNiP with a high quality factor of 551.79 reaches 10.12V/Oe (126.625V/(cmOe)), which is 4.34 times and 19.84 times larger than those of FeFP (2.33V/Oe) and FeMP (0.51V/Oe) composites, respectively. These results provide the possibility of implementing self-biased ME effect in high-sensitivity magnetic-sensing devices.